Stroke is one of the three major causes of death in the United States. Efforts at more sensitive diagnosis of extracranial carotid disease leading to prevention of stroke seem justified. Carotid angiography has 2 disadvantages: it is an invasive study, and it misses as many as 40% of carotid ulcers found at surgery. Our objectives are to develop and demonstrate a method of "intravenous angiography" which has no need for catheters or arterial needles. We will do this 1) by using CT systems, with their increased capacity to image low contrast objects, to image transverse sections of the neck with opacified carotid arteries, and 2) by developing and using novel methods of computer manipulation and display of the information in the transverse images, so as to better show carotid disease. We will present the multiple transvese images via either interactive shaded graphics, by which the iodine column is shown as a rotatable "plaster cast" of the inside of the artery, or by a true 3-D gray-scale display of the entire 3 cm section of the carotid, utilizing the varifocal mirror principle. A typical "vascular" patient will have unenhanced brain CT; then while the standard 4 minute contract infusion is dripping in, 18-24 neck slices of 1.5 mm thickness will be made, to be followed by the enhanced brain slices.